Generally, a temperature sensor of the electronic thermometer senses a body temperature, a detection signal from this temperature sensor is subjected to a signal processing, and then an actual measured temperature is displayed. Since just after starting the measurement, there is a difference in temperature, between the temperature sensor and the body, it takes time to attain a thermal equilibrium state between the temperature sensor and a part to be measured.
Therefore, in the electronic thermometer, an equilibrium temperature in the thermal equilibrium state is predicted based on a variation in the actual measured temperature. The predicted temperature is sequentially updated and displayed, and thereby reducing the measuring time.
This type of electronic thermometer which predicts an equilibrium temperature switches a display of the predicted temperature to a display of the actual measured temperature, when the actual measured temperature approaches the equilibrium temperature, considering an error between the equilibrium temperature and an actual measured temperature.
If this switching from the predicted temperature display to the actual measured temperature display is performed after a lapse of predetermined period of time from the start of measurement, there is a problem of low reliability, since the display switching may be performed even when the actual measured temperature has not attained the equilibrium temperature yet. In order to solve this problem, there has been proposed an electronic thermometer having a function as the following: A difference value between the actual measured temperature and the predicted temperature, or the rate of increase of the actual measured temperature is obtained, and when this obtained value falls into a predetermined range, a timer is set. Until the time set in the timer is up, the predicted temperature is displayed, and thereafter, the display is switched from the predicted temperature display to the actual measured temperature display (see patent document 1).    Patent document 1: Japanese Unexamined Patent Application Publication No. 62-190427